The subject matter disclosed herein relates generally to detecting fault conditions in a motor drive and, more specifically, to utilizing an existing shunt resistor connected to a motor drive to detect the fault conditions.
As is known to those skilled in the art, motor drives are commonly connected between a power source and a motor to control operation of the motor. The input power source may be direct current (DC) or alternating current (AC) and, if the input power source is AC, it may be single-phase or multi-phase and commonly is three-phase. Similarly, the motor may be a DC or AC motor of various types. Consequently, the motor drive is selected according to the power source and type of motor required by a given application. The input of each motor drive is connected to the power source and the output connected to the motor.
A motor drive may be mounted in an enclosure for protection from the elements in an outside application, protection from the operating environment in certain indoor applications, or simply for ease of manufacturing. During assembly of the enclosure, the motor drive may be mounted to a panel at a first station and installed and wired in the enclosure at a second station. Field installation and connection to the input power is performed at a remote location. Because of the numerous configurations of motor drives and the often modular nature of installation, the potential exists for wiring and/or configuration errors when installing, commissioning, or servicing motor drives.
Although motor drives often include sensors and/or detection circuits in an attempt to detect fault conditions, historically, detection does not occur until a run command is issued. Once a run command is issued, sensors detect operating conditions within the motor drive and provide signals corresponding to the voltage and/or current at various points within the drive to a processor and/or logic circuit configured to detect specific fault conditions.
However, some of the fault conditions may be the result, for example, of improper wiring or configuration of the drive. Still other fault conditions may arise if, for example, a fuse or circuit breaker failed between the input power source and the motor drive. Such fault conditions exist prior to attempting to issue a run command. A run command is typically issued when an operator and/or controller desires certain performance from the motor. Further, the motor drive may be part of a system, and other components of the system may already be operating and/or waiting upon execution of the run command by the motor drive. Thus, waiting until the run command is issued to detect these fault conditions may cause unnecessary and undesirable delays in operation.